DASH DIET IMPROVES INSULIN SENSITIVITY AS WELL AS HYPERTENSION

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DASH DIET IMPROVES INSULIN SENSITIVITY AS WELL AS HYPERTENSION

News Author: Laurie Barclay, MDCME Author: Désirée Lie, MD, MSEd

Feb. 6, 2004 — The Dietary Approaches to Stop Hypertension (DASH) diet not only benefits hypertension but also improves insulin sensitivity, according to the results of a study published in the February issue of Diabetes Care.

"As the DASH dietary pattern is implemented as a routine part of non-pharmacologic management of hypertension, it will be important to know the effects on insulin action of a comprehensive behavioral program that includes the DASH dietary pattern," write Jamy D. Ard, MD, from Duke University Medical Center in Durham, North Carolina, and colleagues. "If the addition of the DASH dietary pattern adds to a lifestyle intervention (i.e., weight loss, moderate sodium reduction, and increased physical activity) by increasing insulin sensitivity, such a finding would provide added evidence for the need to recommend the DASH dietary pattern as part of a comprehensive lifestyle intervention for treatment of hypertension and overall cardiovascular risk reduction."

In this ancillary study of PREMIER, 52 subjects were randomized to one of three non-pharmacologic interventions for hypertension. Group A received advice only; the group B intervention included weight loss, reduced sodium intake, increased physical activity, and moderate alcohol intake; and group C received all interventions of group B as well as the DASH dietary pattern. This diet is high in fruits, vegetables, and low-fat dairy products but lower in total fat, saturated fat, and cholesterol. It is replete with nutrients associated with improved insulin sensitivity, including magnesium, calcium, and protein.

Groups B and C had similar decreases in total calories, percentage of calories from fat, and sodium intake, and similar amounts of energy expenditure and weight loss. As expected from the DASH diet, group C had increased intake of protein, potassium, calcium, and magnesium. Compared with the other groups, group C had a significant improvement in insulin sensitivity, from 1.96 to 2.95 (P = .047). Although group B also had a significant decrease in fasting insulin and glucose levels, the changes in insulin sensitivity were not statistically different from those in control subjects.

Study limitations include insufficient power to determine the importance of the change in insulin sensitivity in group B, and the use of two nonconsecutive dietary recalls to estimate nutrient intake.

"Based on the results of this study, including the DASH dietary pattern as a basic part of a hypocaloric dietary plan can lead to significant improvements of up to 50% in insulin sensitivity," the authors write. "This combination of foods and nutrients may have an effect on a variety of different cellular targets that ultimately promotes changes in body composition during weight loss, resulting in a favorable impact on insulin action."

Diabetes Care. 2004;27:340-347

 

 

Learning Objectives for This Educational Activity

Upon completion of this activity, participants will be able to:

 

Describe the benefits of the DASH diet when added to a hypocaloric regimen in hypertensive patients.

List key components of the DASH diet.

Clinical Context

There is evidence that hypertension is associated with abnormal insulin sensitivity in that individuals with essential hypertension also have a higher prevalence of insulin resistance than non-hypertensive individuals, as discussed by Osei and colleagues in the July 8, 1999, issue of the American Journal of Cardiology. However, non-pharmacologic interventions for hypertension suggested by the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure, as discussed in a report in the May 21, 2003, issue of JAMA, do not address the impact of these interventions on insulin action. The recommended interventions include weight loss for overweight individuals, increased physical activity, sodium reduction, and decreased alcohol intake.

The DASH diet also has been recommended for hypertension, and it consists of higher levels of potassium, magnesium, calcium, and fiber than the typical American diet. Sanchez and colleagues, whose research was published in the January 1997 issue of Hypertension, found that 1,500 mg/day of supplemental calcium improved insulin sensitivity in patients with essential hypertension using the euglycemic-hyperinsulinemic pump. Paolisso and colleagues found that magnesium supplementation improved insulin action in elderly patients. Their research was published in the June 1992 issue of the American Journal of Clinical Nutrition.

This report is part of the PREMIER study, a multicenter, randomized clinical trial examining the effects of three lifestyle interventions to reduce high blood pressure. This study was conducted at one of these centers.

Study Highlights

 

Participants were older than 25 years, body mass index (BMI) range of 18.5 to 45 kg/m2 and stage 1 hypertension by Joint National Committee (JNC) criteria.

Exclusion criteria were use of antihypertensive medications, diabetes, weight loss medications, history of cardiovascular event, cancer diagnosis or treatment, and psychiatric hospitalization within 2 years.

Baseline insulin sensitivity was measured using the intravenous glucose tolerance test and repeated at 6 months, at study conclusion. Insulin sensitivity index was calculated.

Weight, height, and waist circumference were measured by standardized methods. Nutrient intake was determined by 2 nonconsecutive 24-hour recalls, and physical activity determined as average metabolic equivalents (METs) by patient questionnaire (self-recall).

52 participants were randomly assigned (as part of the PREMIER protocol) to advice only on one occasion (group A or control; n = 18), intensive behavioral intervention with14 group and 4 individual sessions (group B; n = 16), or intensive behavioral intervention (same number of sessions as group B) with the DASH diet (group C; n = 18) over 6 months.

Participants were provided with the JNC lifestyle intervention guidelines to restrict sodium to 2.4 g or less a day, no more than 30% of calories from fat, weight loss of at least 15 pounds if overweight, and 180 minutes of moderate exercise per week.

Group C participants were advised to restrict caloric intake to 25% or less of fat with 7% or less from saturated fat, 9 to 12 vegetable or fruit servings, and 2 to 3 servings of low-fat dairy per day.

Participants were similar in age (mean, 50 years), sex (67% - 75% female), race (62% -78% non-Hispanic white), BMI (mean, 32 kg/m2), and blood pressure (average, 138/83 mm Hg).

All participants lowered caloric intake, and groups B and C also lowered sodium and fat intake.

Potassium intake for group C increased while intake for group B decreased over 6 months. Dietary intake of magnesium, calcium, and protein showed similar patterns to potassium in group C.

Only group C (the DASH intervention) had an increase in insulin sensitivity of 50% from baseline compared with group B (28% increase from baseline), and no change in group A (P = .047 for groups C vs. A, and P = .146 for groups B vs. A).

The ratio of change for insulin to glucose was almost 3:1 for group C.

30% of all 55 participants achieved 15-pound weight loss (group A, 2 participants; group B, 5 participants; group C, 9 participants). Groups B and C experienced similar amounts of weight loss (5.69 kg vs. 6.56 kg, respectively) vs. 1.18 kg weight loss for group A.

Waist circumference decreased by 5.5 cm for group B compared with no change for group A (P = .06); and it decreased by 7.96 cm for group C vs. group A (P = .005). The difference between groups B and C was not statistically significant.

Alcohol intake was low and did not change for all 3 groups.

Pearls for Practice

 

The DASH diet as part of a hypocaloric dietary pattern with intensive lifestyle counseling can result in improvements of up to 50% in insulin sensitivity.

Intensive behavioral interventions are more likely than advice alone in producing outcomes of weight loss and reduced waist circumference.

 

 

 

 

 

 

 

 

 

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